Simplify the following expression: $k = \dfrac{6a}{5} - \dfrac{a}{7}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $5$ and $7$ $\lcm(5, 7) = 35$ $ k = \dfrac{7}{7} \cdot \dfrac{6a}{5} - \dfrac{5}{5} \cdot \dfrac{a}{7} $ $k = \dfrac{42a}{35} - \dfrac{5a}{35}$ $k = \dfrac{42a -5a}{35}$ $k = \dfrac{37a}{35}$